In industrial automation, functional and logical links between a plurality of devices are usually implemented by wiring the devices together. For this purpose individual connection points of the devices are interconnected by way of a wire in each case (individual wiring). However, such wiring runs the risk of wiring errors at initial installation, is considerably time-consuming to install initially, constitutes a failure risk in respect of the operated automation system (e.g. due to the cables vibrating loose from the connection points of the devices or due to wire contact problems at the connection point) and, in the case of screw terminals, requires maintenance (tightening of the screws at the connection points of the devices).
DE 37 40 290 A1 discloses a device for the open- and/or closed-loop control of processes in which a plurality of electronic building blocks are combined into sub-assemblies which are each disposed on a bus base module. The bus base modules are clamped to a top-hat rail and have laterally in each case a female multipoint connector which is of complementary design to a male multipoint connector having pins. The male and female multipoint connectors are disposed on opposite sides of the bus base module and are open to the front and back respectively of the bus base module. The bus base modules are connected in a movement perpendicular to a longitudinal axis of the top-hat rail. A mechanical and electrical connection between two adjacent bus base modules is established when the latter are consecutively clamped to the top-hat rail.
The publication U.S. Pat. No. 6,081,048 A discloses a modular expandable peripheral unit having a self-establishing electrical connection, the device being suitable for controlling and monitoring a technical process. The peripheral unit comprises expansion module lower parts EMU and base module lower parts BMU which have a profile permitting side-by-side attachments. Disposed in the base module lower parts BMU are contact elements which project from the base module lower parts BMU as a male multipoint connector. Implemented in the expansion module lower parts EMU are openings through which individual pins of a male multipoint connector can be guided. Viewed from the side, the expansion module lower parts EMU and the base module lower parts BMU have an offset profile. The individual pins of the male multipoint connectors which are accommodated in the expansion module lower parts EMU are disposed in the region of an offset stage so as to prevent lateral pulling-apart of the base module lower parts BMU and expansion module lower parts EMU.
DE 71 13 834 A1 discloses a holder for a plurality of side-by-side disposed electrical equipment units which are each assigned a holder section. Each holder section comprises a base component, a surface of which has mechanical ways of detachably mounting the equipment units. In addition, on opposite lateral surfaces, each base component is provided with mutually complementary connection projections and insertion recesses which are connected to electrical line projections. The electrical line projections allow inserted equipment units to be supplied with electric power. Adjacent base units can be electrically interconnected by being plugged into one another.
U.S. Pat. No. 4,790,762 A discloses an expandable wiring backplane which is designed to accommodate and interconnect electrical equipment units. The wiring backplane comprises a plurality of essentially identical backplane modules which are provided on opposite lateral surfaces with centering pins and tubular recesses in a complementary manner. In addition, electrical blade contacts and contact strips are mounted on opposite side walls of a backplane module. When two backplane modules are pushed together, the centering pins in the tubular recesses ensure that the backplane modules are mechanical aligned to one another. The blade contacts and contact strips of adjacent backplane modules are implemented in alignment with one another so that, when the backplane modules are pushed together, an electrical connection is established between them. Equipment units which are inserted in the backplane modules at right angles to the backplane are supplied with power via this electrical connection. The equipment units inserted in the backplane modules are secured with screws during assembly and their footprint essentially covers the entire user-facing surface of the backplane module.
WO00/25560 A1 discloses a modular connection system for electrical devices which comprises modular mounting units 50 which are fastened to a top-hat rail. On their lateral surface, the modular mounting units have contacts which are designed to establish an electrical connection to an adjacent modular mounting unit. Connections for signal transmission are additionally implemented on the lateral surfaces of the modular mounting units. An electrical device can essentially be inserted perpendicularly to the top-hat rail on an individual modular mounting unit. The modular mounting units are each provided with a toothed rack and a driving pinion. The toothed rack and driving pinion of adjacent modular mounting units engage with one another and ensure interlocking of adjacent modular mounting units on the top-hat rail.
If a safety application is covered by the automation system (e.g. EMERGENCY-STOP shutdown, protective door monitoring or protection of presses or punches), the safety switching devices used in the safety application must fulfil heightened safety requirements. Such safety switching devices are e.g. the SIRIUS 3TK28 equipment made by SIEMENS. By way of such safety switching devices, the following safety oriented functions in particular can be provided:                monitoring of the safety functions of sensors,        monitoring of sensor lines,        monitoring of the correct operation of the safety switching device,        monitoring of actuators for standstill,        safety oriented shutdown of hazards.        